(327f) Photochemical Adaptable Networks

Chemically crosslinked networks are typically described as thermosets, owing to their inability to be melted or molded. Here, we incorporate reversible covalent linkages throughout the network backbone to facilitate controllable bond rearrangement and material reshaping. Specifically, we incorporate allyl sulfide functional groups, which are capable of undergoing photo-induced reversible addition-fragmentation chain transfer. In these materials, both the post- and during-polymerization stress reduction are observed. The novel stress relieving properties of post-polymerized networks are demonstrated by the reshaping and actuation of the material. During-polymerization stress reduction is demonstrated in the thiol-ene resin using a photo-tensometer coupled with an infrared spectrometer that provides real-time functional group conversion information. These measurements strongly support the proposed reversible addition-fragmentation chain transfer mechanism and further demonstrate significant stress relaxation via bond rearrangement in the latter stages of polymerization (i.e., post gel-point).